The present invention relates to an apparatus and method for controlling fuel injection in an internal combustion engine that has an in-cylinder injector for injecting fuel into a combustion chamber and an intake system injector for injecting fuel into an intake system.
There is known an internal combustion engine provided with an in-cylinder injector for directly injecting fuel into a combustion chamber of an internal combustion engine and an intake system injector for injecting fuel into an intake system such as an intake port or a surge tank (Japanese Laid-Open Patent Publication No. 2001-73854).
In the internal combustion engine described in this Japanese Laid-Open Patent Publication No. 2001-73854, under the control of fuel injection in the engine starting state, fuel is first injected from an intake system injector for a predetermined time period. Then, fuel is injected from an in-cylinder injector. By executing such control of fuel injection, an initial explosion, that is, the first combustion of air-fuel mixture in the combustion chamber is performed by fuel injected into an intake system. Thus, since temperature within the combustion chamber rises after the initial explosion, vaporization of the fuel injected from the in-cylinder injector is promoted. Therefore, according to the control of fuel injection in the engine starting state described in the Japanese Laid-Open Patent Publication No. 2001-73854, it becomes possible to restrain the fuel injected from the in-cylinder injector in the engine starting state from being discharged as an unburned component.
When injecting fuel into the intake system, it takes some time period for the fuel injected to flow into the combustion chamber. For this reason, in the above-described conventional internal combustion engine, the initial combustion of the air-fuel mixture in the combustion chamber in the engine starting state, that is, an initial explosion becomes late, and there is a possibility that the engine startability becomes deteriorated.
In this case, when fuel is directly injected into the combustion chamber in the engine starting state, it is possible to shorten a time period required between the fuel injection and the initial explosion, and to ensure favorable engine startability. When, however, the temperature within the combustion chamber is as low as when the engine is started, the fuel directly injected within the combustion chamber easily adheres to the inner wall of the combustion chamber and the piston, and there is a possibility that this adhered fuel is discharged as an unburned component.